Inventory management @ project site

Dear Friends

We are doing customer project. Most of my client's project are Turn key projects, which usually run for 2-3 years. In the span of project life, lots of materials at different stages will be procured & will be dispatched to project site from Vendor. Once GR is done at the project site, invoice verification & payment will be made.

Now my client wants to maintain inventory of all the material @ project site with material value.

For example: On 2nd April 2009, 100 nos. of XYZ material received @ project site worth Rs.100000.

On 10th April, 25 no of XYZ are consumed for project activity worth Rs.25000.

My client wants to monitor all these activities on the system. According to him, after consumption of 25 no. of XYZ material worth Rs.25000, System should show the remaining material as 75 no. of XYZ material worth Rs.75000 is still available in the stock.

Now say, if Vendor dispatches another 100 XYZ material, system should update the stock available as 175 no. of XYZ are available.

How can it be achieved?

Because in SAP system, once we make vendor payment, its no more our responsibility. It's customers material.

But here, after payment to vendor, customer is giving back these material to us, to execute the project.

Please suggest the possible solution.

Thanks & Regards